I am putting this in the PicoScope forum because a good information system is an essential component of Lab Scope Diagnostics.
There are a few to choose from but IMHO Alldata is the single most complete source of factory information available.
Sure, even factory information has occasional errors, but it doesn't get any better than that. Component and system descriptions are not generic, but vehicle-specific. This is essential when working with a system that you may not be entirely familiar with. Some may not like working with different wiring diagram formats from different manufacturers, but when you need to locate a component, connector, pin or wire you are likely to get just what you need.
I can't count the number of times I have helped someone out who was on a wild goose chase due to incomplete or incorrect information from another system. That costs money. If they had good information to begin with, the repair would have gone much more smoothly and been more profitable.
If you are like me, I make enough mistakes on my own. I don't need any help from my information system.

I recently switched over to Alldata Online and I absolutely love it. It's so much quicker than the disks and you don't have to fumble around for the right disk. Plus, you can have more than one PC that can access Alldata on your shop network. Awesome.
This may sound like an advertisement, but I am not connected with Alldata or paid for sending them business. But...tell them I sent you anyway. Hopefully, they won't charge you any extra because of that
http://www.alldata.com/products/online/